The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Typically, fluid systems are periodically checked for leaks. For instance, a vehicle evaporative fuel system is typically checked for leaks to insure emission compliance, etc.
Some fuel systems include a switch that automatically changes state according to pressure in the vehicle evaporative fuel system, and the presence of a leak is determined according to the switch behavior. For instance, many fuel systems include a vacuum switch that automatically changes state to a CLOSED configuration (i.e., an OH configuration) under a vacuum. When the ambient temperature is decreasing (e.g., at night), a vacuum is created in the fuel system, thereby switching the vacuum switch from OPEN to a CLOSED configuration. An on-board computer monitors that the vacuum switch closes as expected, if the vacuum switch fails to close, a vacuum has not been created, and a leak is thereby detected.
However, this method of leak checking can take a significant amount of time, making it inappropriate for some situations. Thus, in order to check for leaks in less time (e.g., during vehicle assembly), an external tool is coupled to the fuel system to either increase or decrease pressure in the system, and then the system is monitored for significant pressure changes indicative of a leak. However, this testing method can be relatively expensive, can require large and complicated equipment, and can take a significant amount of time.
Thus, it has been proposed to couple a relatively simple pump to the fuel system, create a vacuum in the system, and then monitor the vacuum switch to check for leaks in the fuel system. If the switch remains closed for a predetermined amount of time, then the system is determined to have adequate integrity, and if the switch opens within the predetermined amount of time, the system is determined to have a leak larger than allowed.
However, the vacuum switch may not switch consistently, especially under the influence of small changes in vacuum. More specifically, the vacuum switch may switch at varying times in the presence of the same size leak, thereby reducing the accuracy of the leak check processes. Accordingly, there remains a need for a fluid system leak testing assembly and method that is simpler, less expensive, faster, and more accurate than the prior art.